Preparation of 2-amino-4-hydroxy-6-formyl pteridine



Patented Aug. 1, 1950 PREPARATION OF Z-A .FQRMYL PTEBIIDINE r Coy W. waiiaran River,"Nl*Y., assignor to American (lyanamid Compani New York; N. Y.,'. a corporation of Maine No Drawing. Application February 4, 1949,

w Serlal No. 74,720 (1 This invention relates to a new and improved process for the preparation of z-aminoe-hydroxy-G-formyl pteridine. i l i The compound, Z-amino-d-hydroxy;G-formyl pteridine, is a known compound, its"'preparatiouhaving been described by the present inventor and co-workers in the Annals of the -New. York .Academy of Science, vol. XLYI II, article 5,.pages273-277. This article disclosesgthe preparation of this compound by the degra ation of the product obtained 1 by the aerobicfermentationyof a bacterium of the genus Corynebacterium with sulfurous acid. This method of obtaining the formyl pteridine obviously does not lenditself to a synthetic commercial method for the preparation of pteroylglutamic acid utilizing the Z-amino-4-hydroxy-6-formyl pteridine as. an intermediate. e

I have found that this formyl pteridine can be obtained in good yields by the hydrolysis of 2- amino 4 -hydroxy-S-dibromomethyl pteridine. This hydrolysis may be carried out at a pH of about A; to by mixing the dibromomethyl pteridine with a hydrolytic solvent.

The hydrolysis may be carried out using the dibromomethyl pteridine or an acid salt thereof. When using an acid salt it is preferable to dissolve the salt in a small amount of a'solvent such as formic acid, methyl Cellosolve,';.and the like. This is then added to water. However, the salt or the base can be dissolved in an aqueous strong acid which is then mixed with water. When using an aqueous strong acid better results are usually obtained by adding a basifying substance such as sodium acetate, sodium hydroxide, potassium hydroxide, etc. in order to bring the pH to within the preferred range of pH 2 to pH 8.

The reaction may be carried out at, a temperature within the range of about C. to about 120 C. The time of reaction varies from a few minutes to about one hour, depending upon the temperature used.

The 2 amino 4 hydroxy-G-dibromomethyl pteridine, used as an intermediate in the present invention, may be obtained by the bromination of the corresponding S-methyl pteridine as described and claimed in a copending. application of James H. Boothe, Serial Number 35,069, filed June 24,1948.

The 2-amino-4-hydroxy-6-for1nyl pteridine is useful as an intermediate in the preparation of pteroylglutamic acid. The reaction of this intermediate with para-aminobenzoylglutamic acid to produce pteroylglutamic acid is described and claimed in a copending application of Brian L.

menses; sen i nsins r 73,440 filed January 28,1949. r

orderto illustrate some aspects of the inverition in greater detail, the following examples ar givencwhich describethe preparation of the intermediate 2 amino 4 -hydroxy-6-dibromcmethyl pteridine from the, corresponding 6-. methyl pteridine and the use of this intermediate to prepare the 2-amino-4-hydroxy-6--Iormy1 pteridinep. l

r .Ewm l r g. of2 amino-4-hydroxy-B-methyl pteridine, 1%: liters 0f'.48% hydrobromic acid and 310 g. ofwbromine aremixed and stirred at steam bathiemperature .fonz hours. A 300 cc. portion-.isevaporated off under reduced. pressure. The solution is cooled and clarified wth charcoal. The filtrate, after concentrating under reduced pressure to 600 cc. and cooling, deposited 79 g. of essentially pure '2-amino4 hydroxy-B-dibromomethyl 'pteridine hydrobromide. One gram "of Z aniino-4 hydroxy-6-dibromo methyl-pteridine hydrob'romide is dissolved in 50 cc. of methyl Cellosolve. This solution mixed with 1 liters of boiling water. The mixture is stirred at the boiling temperature of the mixture for 20 minutes. After cooling, the product, 2- amino-4-hydroxy-6-formyl pteridine, is filtered off, washed and dried.

Example 2 Two grams of Z-amino-4-hydroxy-6-methyl pteridine, 100 cc. of 48% hydrobromic acid and 14 g. of bromine are mixed and heated in a sealed tube in a steam bath for one hour at 100 C. and in an oil bath at C. for a half hour. After standing overnight, a 5 cc. sample is titrated with standard sodium thiosulfate solution which shows that 1.7 moles of bromine has reacted. The excess bromine is evaporated off under vacuum from the remainder of the reaction mixture. The resulting solution, after chilling, is filtered free of some unreacted 'pterin. The filtrate is concentrated to about one-third volume under reduced pressure and chilled overnight. Again the solution is filtered and the filtrate concentrated to dryness under vacuum. The residue is predominately 2 amino 4 4 hydroxy-G-dibromomethyl pteridine hydrobromide.

The residue is dissolved in 164 cc. of water which contained enough hydrochloric acid to effect solution. Two-thirds of this solution is heated to boiling and bufiered to about pH 4 by using sodium acetate. After cooling the 2- amino-l-hydroxy-fi-formyl pteridine is collected,

The red phenylhydrazone forms immediately. It

is filtered off while the mixture is hot, washed and dried; weight 100 mg. n analysis'for carbon,

hydrogen and nitrogen the values agree closely amino-i-hydroxy 6 dibromomethyl with the theoretical values for the phenylhydrazone of Z-amino-4-hydroxy-6-formyl pteri-,

dine.

Example 3 Twenty grams of Z-amino-i-hydroxy-fi-methyl pteridine and 12 cc. of bromine in 1 liter of 48% hydrobromic acid is refluxed for 1 hour to effect solution and to-complete the-bromination. This solution is concentrated to 500 cc. under vac uum-w The concentrated solution is treated with 21 g. of activated charcoal and run into 3% liters of cold water. This diluted aqueous solution is precipitated with enough sodium acetate to bring to pH 3 to 5. The Z-amino--hydroxytj-dibromomethyl pteridine is isolated and dried; weight 24 g.

Four grams of the above product is dissolved in 200 cc. of 6 N hydrochloric acid with gentle warming; This solution is poured into 4 liters of boiliiig water. The resulting solution is treated with sodium acetate until a pH 5 to 6 is obtained. After cooling the solution, the 2-amino-4-hydroxy fi-form'yl pteridine is collected and dried; weight 2.5 g.

. Example 4 Another-experiment is carried out as described in Example 1 with the exception that formic acid is used in place of methyl Cellosolve. The product obtained is 2-amino-i-hydroxy-fi-formyl pteridine.

Iclaim:

1. A method of preparing 2-amino-4-hydroxyfi-iormyl pteridine which comprises mixing a member of the group consisting of 2-amino-4- hydroxy-S-dibromomethyl pteridine and salts thereof with an aqueous solution.

.2. A method of preparing z-amino-l-hydroxy- 6-formy1 pteridine which comprises mixing 2- pteridine with an aqueous solution at a temperature within the range of 5" C. to about 120 C.

3. A method of preparing 2-amino-4-hydroxyfi-formyl pteridine which comprises mixing a member'of the group consisting of 2-amino-4- hydroxy-fi-dibromomethyl pteridine and salts thereof Withan aqueous solution for a period of from I5 minutes to one hour at a temperature of 4., A method of preparing Z-amino--hydroxyfi-formyl pteridine which comprises mixing 2- aminol hydroxy' 6- dibromomethyl pteridine with an aqueous solution inthe presence of sodium acetate for a period of from 5 minutes to one hour at'a temperature of from 15 C. to about 120 C.

5 A method of preparing 2-amino-4-hydroxyfi-formyl pteridine which comprises dissolving 2- amino-4-hydroxy-6 dibromomethyl pteridine in water in the presence of a mineral acid, adjusting the pH to Bto fi with sodium acetate and after 5 minutes to one hour at a temperature of from 15 C. to about 120 C., recovering the 2-amino-' 4-hydroxy-6-formy1 pteridine therefrom.

6. A method of preparing 2-amino-4-hydroxy- 6-formyl pteridine which comprises dissolving 2- .amino-4-hydroxy-6-dibromomethyl pteridine hydrobromide in methyl Cellosolve, mixing said -1 lution with Water for a period of from 5 minutes to one hour at a temperature of from 15 C. to 'C. and recovering the 2-amino-4-hydroxy 6-formy1 pteridine therefrom.

COY W. WALLER.

No references cited. 

1. A METHOD OF PREPARING 2-AMINO-4-HYDROXY6-FORMYL PTERIDINE WHICH COMPRISES MIXING A MEMBER OF THE GROUP CONSISTING OF 2-AMINO-4HYDROXY-6-DIBROMOMETHYL PTERIDINE AND SALTS THEREOF WITH AN AQUEOUS SOLUTION. 